The European Union slapped revenge tariffs on iconic US products including bourbon, jeans and motorcycles on Friday in its opening salvo in a trade war with President Donald Trump.
Within hours, Trump responded with a threat to impose a 20 percent tariff on cars imported from the European Union.
The EU tariffs, which took effect at midnight (2200 GMT Thursday) according to the EU's official journal, will further fuel jitters on world stock markets that are already alarmed by trade tensions between the United States and China.
Customs agents across Europe's colossal market of 500 million people will now impose the duty, hiking prices on US-made products in supermarkets and across factory floors.
"These measures are the logical consequence of the US decision," French Finance Minister Bruno Le Maire told AFP.
"They reflect a Europe that is resolute and principled," he said.
Brussels imposed the raft of duties on US products worth 2.8 billion euros ($3.3 billion) in a tit-for-tat response to Trump's decision to slap stiff tariffs on European steel and aluminium exports.
Global markets on Friday took the development in their stride, with stocks in Europe firm after weeks of instability on trade worries.
EU Trade Commissioner Cecilia Malmstrom said this week that the 28-nation bloc was "left with no other choice" but to impose tariffs of its own after the "unilateral and unjustified decision of the US."
Together with US tariffs against Mexico and Canada, the trade battles have raised the spectre of a global trade war, spooking financial markets that fear major consequences to the global economy.
"We have a trade war -- and it's an escalating trade war," SEB chief economist Robert Bergqvist told AFP in an interview.
John Ferguson, director of global forecasting at the Economist Intelligence Unit agreed, as he sounded a warning about the US trade disputes rumbling on the EU and Chinese fronts.
"Mr Trump has now opened up two fronts of this conflict and both have the potential to escalate out of control," Ferguson said.
The list of goods subject to EU duties does not specifically name brands but European Commission chief Jean-Claude Juncker spelled out in March that the bloc would target "Harley-Davidson, bourbon and Levi's jeans".
Cigarettes, cranberries, cranberry juice, orange juice, sweetcorn and peanut butter are among the other products targeted.
Juncker said on Thursday that the US decision to impose tariffs "goes against all logic and history".
"Our response must be clear but measured. We will do what we have to do to rebalance and safeguard," he said.
European consumers would be able to find "alternatives", European Commission Vice President for trade Jyrki Katainen said.